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What is a Captcha

By Heshy Friedman

A captcha is a random series of letters and/or numbers that a web form asks you to enter. Captchas were developed to ensure that human beings are the ones submitting the form rather than bots. Bots are configured by spammers to send out junk using contact forms. They do this by writing a script that scans the web for forms, and automatically fills out all the fields with garbage and submits it. This sends the contents of the spam-filled form as an email to the site administrator.

A captcha’s function is to eliminate the ability of these scripts to submit a form. The form will only submit if the correct characters are entered into the captcha field, and an automatic spam bot has no way of knowing this. Since it is computer-generated script, the bot is unable to process and submit the form, thereby eliminating the spam.

While not entirely foolproof, captchas have become essential for public web forms. Without a captcha, an open form will almost inevitably be found by spamming bots and preyed upon. Due to the explosion of spammers and hackers, spammers will eventually find their way to an unprotected form and submit garbage to it. All public forms I create today are secured by a captcha, although some are hidden, which I will discuss at a later date.